In recent years, in order to deal with a lot of data, the number of various types of information-processing equipment having a built-in memory device, such as a hard disk, has increased. For example, in printers and copy machines, it has become common that received printing data, image data read out through a scanner, output image data, and the like are temporarily held in a hard disk, and printing processing is carried out while reading out such data.
When, in a printer or a copy machine, printing was completed, received printing data and image data that had been held in a hard disk have been deleted; however, such data was merely deleted from a management area that is referred to as FAT (File Allocation Table). In other words, logically, image data was deleted, but, physically, it was left in a hard disk.
With data being left in a hard disk, when the equipment itself or the hard disk is sneaked out, or when the data is illegally accessed through other information-processing equipment connected to the network, there is a risk that information leaks.
In order to eliminate the risk of information leakage due to residual data, files that are no longer required have to be physically erased. In this situation, “physical erasure” of a file, for example, denotes overwriting of a corresponding storage area, by means of data that itself has no specific meaning. Hexadecimal “00” or “FF” may be used for overwriting; however, in the case of a magnetic recording device such as a hard disk, data that has previously been recorded may be read out, due to residual magnetism. For more robust security, by implementing overwriting several times through irregular random numbers, traces of the data, due to the residual magnetism, have to be completely erased.
To date, in an apparatus, such as a printer and a copy machine, allegedly providing security measures, out-of-use files have been physically erased. In order to minimize the risk of information leakage, it is ideal that files that were used and are no longer required are immediately and physically erased; however, as described above, in physical-erasure processing, overwriting processing is applied to a file several times, whereby, in the case where the size of the file is large or the number of the file is large, the processing takes a long time, thereby posing a problem that processing of the following page is delayed.
In this regard, several technologies have been disclosed in which timing at which the physical erasure of a file is implemented is controlled so that processing for implementing physical erasure of a file (information) does not affect the following information processing.
Japanese Patent Laid-Open No. 9-284572 has disclosed an approach in which, in the case where processing having priority higher than that of the physical erasure of a file is implemented, the physical erasure is interrupted, or the physical-erasure processing of the file is kept undone until the printing apparatus comes into an idle state. In addition, Japanese Patent Laid-Open No. 2003-037719 has disclosed an approach in which a time zone for implementing the physical erasure of a file is controlled, based on a history of past operation.
However, the technologies disclosed in the foregoing patent literatures 1 and 2 are eventually to delay the timing of implementing physical erasure of files that have been left within a memory device such as a hard disk, so that the effect of the physical erasure, on the following data processing, is diminished; accordingly, the delay of implementation of physical-erasure processing of a file may leads to increase in opportunity of information leakage due to illegal access, thereby opposing the original object, i.e., preventing information in the memory device from leaking out. Moreover, the longer the data processing continues, the more data remains in the memory device; thus, a lot of information is exposed to the risk of leakage.
Still moreover, files that have been used and are no longer required remain in the memory device until the physical-erasure processing is implemented, thereby reducing a margin of the storage area of the memory device; therefore, there is a problem in that, in order to avoid this, a large-capacity memory device has to be mounted that includes the capacity corresponding to the margin, for the storage area, that is reduced due to consideration of security, in addition to the capacity of the memory device in the case where securing of the security is not taken into consideration. This problem becomes more conspicuous in apparatuses that continually treat full-color images, having many pixels, and the like.
Furthermore, there is a problem in that, because, in file management for a magnetic memory device such as a hard disk, as the physical-erasure processing of a file, overwriting processing, through random numbers, applied to storage areas is implemented several times, the lifetime of the memory device is drastically shortened.
Therefore, it is an object of the present invention to realize an effect equivalent to the physical-erasure processing, by, in an image processing apparatus such as a printer and a copy machine, preferentially utilizing, as an area for storing data, an out-of-use storage area in a memory device such as a hard disk, instead of simply making the out-of use storage area be a target of physical-erasure processing; it is also an object of the present invention to realize securing of security that is robuster than those of conventional technologies and to provide an image processing technology that has no adverse effect, for example, delaying the following data processing.
Moreover, it is an object of the present invention to provide an image processing technology that makes it possible to prevent reduction, of a margin of the storage area of the memory device, that is caused by accumulation of data to which the physical-erasure processing is to be applied, by utilizing storage areas for out-of-use files, in priority to free areas, and by making the storage areas store data.
Still moreover, it is an object of the present invention to provide an image processing technology that enables reduction of the number of overwriting processing for physical-erasure processing and that enables minimizing of decrease in the lifetime of a memory device, by preferentially utilizing out-of-use storage areas, as areas for storing data, instead of simply making the out-of use storage areas be objects of physical-erasure processing.